The general goal of these investigations is to explore the impact of ischemia induced during the course of cardiopulmonary bypass on ventricular performance. More specifically, ischemic injury will be quantitated in terms of alterations in the diastolic properties of the left ventricle as reflected by alterations in the pressure volume relationship as an expression of chamber stiffness and of alterations in stress-strain properties as an expression of specific muscle stiffness. The technique to be employed for assessment of diastolic properties involves dimension measurement using pulse transit ultrasound with matched pairs of piezoelectric crystals placed in dog models along the major axis, minor axis and mid-wall thickness of the ventricle. For patient studies analysis will be limited to minor axis and wall thickness at the equatorial minor axis. These changes will be correlated with the presence or absence of ischemic contracture, specific degrees of biochemical injury as measured by alterations in myocardial high energy phosphate content and mitochondrial function. Alterations in diastolic properties will be correlated with the extent to which systolic performance is impaired as measured by contractile indices during isovolumic systole as well as ejection indices, all corrected for the diastolic abnormalities by performing measurements at isolength points. Studies will be performed in dogs and rats with normal hearts as well as model of canine valvlar aortic stenosis and ventricular hypertrophy in hypertrophied rat hearts produced by supravalvular banding. Data will be acquired in the experimental models by studying the effects of progressively greater periods of global ischemia on diastolic properties and then by allowing reperfusion and assessing reversibility or intensification of abnormalities in diastolic properties and the accompanying changes in systolic properties and biochemical constitution of the hearts.